Many consumer packaging applications employ containers, such as disposable bags and reclosable plastic bags.
Mass producing plastic bags often involves sealing and cutting or perforating a moving film of polymeric (plastic) material. Other processes or operations may be involved in the production of certain types of plastic bags. Some conventional techniques for producing plastic bags involve performing these processes using a series of forming elements that engage the moving film for a limited amount of time. Because the period of engagement between a given forming element and the film is limited, the process, e.g., sealing, performed by the forming element must be accomplished fairly rapidly. These time constraints potentially compromise the quality of certain processes. For example, a sealing element might form an undesirable or unacceptably high number of incomplete seals.
In order to address these problems, techniques have been proposed to increase the time period during which a forming element is in contact with the portion of the film on which the corresponding process is performed. Some machines, for example, use rollers to adjust this amount of time. This adjustment has typically been performed with the machine stopped. Furthermore, adjusting, for example, the distance between seals on the film has typically involved installing a seal drum of a different diameter. This installation is difficult to perform while the film is running, limiting the ability to change bag and zipper skirt lengths on the fly.